1. Field of the Invention
The present invention is directed to a carbide-tipped drill bit and a method for manufacturing the bit which produces consistent, single helix geometries.
2. Description of the Relevant Art
Carbide-tipped drill bits are generally produced by cutting, heat treating, and centerless grinding steel rod stock which is to be used as a drill bit. Subsequently, flutes having a desired helix angle are ground in the exterior surface of the rod which is subsequently finish ground and cleared to produce the blank from which the carbide-tipped drill bit will be manufactured.
Following production of the blank, the manufacturer slots the tip end of the fluted blank at a predetermined angular position and depth to accommodate proper insertion of a carbide tip blank. The blank is brazed into the slot and the face and margin are then hand blended into the original flute geometry and finishing operations are performed.
The second grinding operation, which blends the carbide tips into the pre-existing flutes is generally carried out by hand using a diamond cutting wheel. The result of the hand operation is a second helix angle, or "roll-back," where the flute helix approaches the tip. This second helix angle varies from drill bit to drill bit and prevents the manufacturer from achieving batch consistency. Additionally, the second grinding operation must be done manually, thereby increasing production time and cost. Due to the blending operation, most manufacturers of carbide-tipped drill bits are limited to one, or a few standard drill geometries due to the need to set up machining which is specific for the hand blending operation and the flute geometry. This limits flexibility regarding the provision of unusual or special application flute geometries.
The present invention is directed to a method of producing a carbide-tipped drill bit which addresses the problems described above.